Scheme selection of anti-surge control system for centrifugal compressor
The research of anti-surge control system should be combined with existing technology.
A. The application of frequency conversion technology can effectively reduce the possibility of surge. Using variable frequency speed regulation technology, it is possible to adjust the operating conditions of the compressor by changing the working frequency of the drive motor, adjust the speed of the compressor, and reasonably adjust the operating conditions of the compressor to meet the flow demand, reduce the operating power of the compressor, and realize the control of the surge phenomenon and ensure The safety of the crew and personnel reduces energy consumption to a certain extent, and keeps noise as much as possible within an acceptable range. However, variable frequency control requires high investment and maintenance costs for variable frequency motors and supporting variable frequency systems.
B.The compressor outlet flow is returned to the inlet through the return pipeline to compensate for the excessively small inlet flow to prevent surge. An anti-surge valve is usually installed on the return pipeline. In the early stage of operation, the anti-surge valve is fully opened to ensure sufficient inlet flow compensation; after stable operation, the pipe network flow is sufficient, and then the valve is slowly closed to meet the rated working conditions. At the same time, when surging occurs, it has a quick opening function to prevent surging to the greatest extent.
C. Anti-surge control system with imported regulating vane + backflow control. For air separation equipment, due to the large inlet flow, an inlet adjustable guide vane is usually installed at the front end of the first stage impeller inlet of the compressor, and the guide angle can be adjusted according to the work needs. Generally, the design flow rate is 45-100% as the control range. The minimum control value depends on the gas input and output status (pressure, inlet temperature, outlet temperature and gas composition), as well as the position of the guide vanes (inlet guide vane, outlet diffuser). Guide vanes with different angles correspond to different working curves . When the reflux is not turned on, the flow adjustment range can reach 45-100%, without surge. When the compressor operating point is close to the surge limit, surge control and surge protection are activated.
Therefore, imported adjustable guide vane + return flow control is an energy-saving, simple and easy anti-surge control scheme. However, the inlet guide vane adjustment is mostly used in air compressors, and for special models that are not suitable for installing imported guide vanes, such as propylene refrigerant compressors, it can only be controlled by reflux. For sites that do not have steam conditions and cannot use steam turbines, variable frequency motors or couplers can be selected to achieve the anti-surge function of variable speed regulation.